The present invention relates to the enhancement of skin color signals included in video signals, and more particularly relates to a circuit which enhances the reproduction quality of skin color in video signals in response to average luminance levels of video signals, skin color area in the video signals, and average luminance level of skin color in video signals. Further, the present invention relates to an improvement in a circuit which enhances the reproduction quality of skin color in video signals in response to skin color area in video signals, average luminance level of skin color in video signals and average luminance levels in video signals.
Recently, a television receiver (TV) with a wider than normal screen has drawn significant attention in the market. Consequently, the demand on picture quality has become more severe. Since human eyes are particularly sensitive to skin color reproduction, skin color reproduction capability greatly influences picture quality.
The prior art for improving the reproduction quality of skin color signals in video signals is described below. FIG. 4 is a block diagram of a skin-color-luminance enhancement circuit in accordance with the prior art.
Average luminance-level detector 3 detects an average luminance level of an input video signal. When video luminance signal of one frame is integrated, an average luminance for one frame results.
Skin-color-waveform detecting circuit (hereinafter called "detector") 7 detects a skin color signal from a color-difference-signal of a received video signal. The average luminance output from average- luminance-level detector 3 and the skin-color waveform output from the skin-color waveform detector 7 are transmitted to skin-color-waveform correction circuit (hereinafter called "corrector") 8.
An output of a correction signal from the color-waveform-corrector 8 is transmitted to a luminance-signal-corrector 9, where a correction signal is added to the luminance signal before being output.
A conventional skin-color-luminance enhancement circuit so structured enhances the skin-color-luminance level in response to an average luminance level of the video signal. However, skin color is darkened and dimmed by secondary effects from Auto Contrast Level which adjusts beam intensity from a cathode ray tube (CRT) and Black Level Enhancement which adjusts a black level in the video signal.
According to this conventional structure, skin color is corrected by using only the average luminance level of the video signal. Thus, skin color is not adequately corrected in response to skin color condition. Consequently, gradation on skin color is not fully displayed, because an average luminance level of the video signal may stand at a high level even if the luminance level of skin color is maintained at a high level. This further boosts the skin-color luminance.